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The ability to accurately predict traffic loading is essential for cost-effective bridge maintenance and repair programs. The traffic load model currently used in the United States for the design of long-span bridges was developed over three decades ago. In the meantime vehicle characteristics and traffic patterns have changed. The Eurocode for traffic loading is more recent, but was calibrated only for bridges up to 200 m long. In this work, Weigh-In-Motion traffic records from 11 different sites across Alabama are used to establish congested traffic loading. Traffic microsimulation is used to generate the congestion, based on the real traffic data. Influence lines for two typical long-span bridges – one cable-stayed and one suspension bridge – are determined using finite element models. These are used in the microsimulation model to estimate the bridge load effects caused by congested traffic. These results are extrapolated to find characteristic lifetime maximum values which are used to evaluate the Eurocode load model to assess its suitability for long-span bridges. In a similar way, the current American load model for long-span bridges, commonly known as the ASCE model, is evaluated to see if it accurately reflects the congested traffic loading that is currently found on American highways. Recent research has suggested the use of the AASHTO HL-93 load model to estimate the effects of traffic loading on long-span bridges, and this model is also evaluated in this work.
Enright, B., Carey, C., Caprani, C.C. (2013), ‘Microsimulation Evaluation of Eurocode Load Model for American Long-Span Bridges’, Journal of Bridge Engineering, ASCE, in print, doi:10.1061/(ASCE)BE.1943-5592.0000546